/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.jmx.access;

import java.beans.PropertyDescriptor;
import java.io.IOException;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.net.MalformedURLException;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import javax.management.Attribute;
import javax.management.InstanceNotFoundException;
import javax.management.IntrospectionException;
import javax.management.JMException;
import javax.management.JMX;
import javax.management.MBeanAttributeInfo;
import javax.management.MBeanException;
import javax.management.MBeanInfo;
import javax.management.MBeanOperationInfo;
import javax.management.MBeanServerConnection;
import javax.management.MBeanServerInvocationHandler;
import javax.management.MalformedObjectNameException;
import javax.management.ObjectName;
import javax.management.OperationsException;
import javax.management.ReflectionException;
import javax.management.RuntimeErrorException;
import javax.management.RuntimeMBeanException;
import javax.management.RuntimeOperationsException;
import javax.management.openmbean.CompositeData;
import javax.management.openmbean.TabularData;
import javax.management.remote.JMXServiceURL;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.BeanClassLoaderAware;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.core.CollectionFactory;
import org.springframework.core.MethodParameter;
import org.springframework.core.ResolvableType;
import org.springframework.jmx.support.JmxUtils;
import org.springframework.jmx.support.ObjectNameManager;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;
import org.springframework.util.StringUtils;

/**
 * {@link org.aopalliance.intercept.MethodInterceptor} that routes calls to an
 * MBean running on the supplied {@code MBeanServerConnection}.
 * Works for both local and remote {@code MBeanServerConnection}s.
 *
 * <p>By default, the {@code MBeanClientInterceptor} will connect to the
 * {@code MBeanServer} and cache MBean metadata at startup. This can
 * be undesirable when running against a remote {@code MBeanServer}
 * that may not be running when the application starts. Through setting the
 * {@link #setConnectOnStartup(boolean) connectOnStartup} property to "false",
 * you can defer this process until the first invocation against the proxy.
 *
 * <p>This functionality is usually used through {@link MBeanProxyFactoryBean}.
 * See the javadoc of that class for more information.
 *
 * @author Rob Harrop
 * @author Juergen Hoeller
 * @see MBeanProxyFactoryBean
 * @see #setConnectOnStartup
 * @since 1.2
 */
public class MBeanClientInterceptor
        implements MethodInterceptor, BeanClassLoaderAware, InitializingBean, DisposableBean {

    /**
     * Logger available to subclasses
     */
    protected final Log logger = LogFactory.getLog(getClass());

    @Nullable
    private MBeanServerConnection server;

    @Nullable
    private JMXServiceURL serviceUrl;

    @Nullable
    private Map<String, ?> environment;

    @Nullable
    private String agentId;

    private boolean connectOnStartup = true;

    private boolean refreshOnConnectFailure = false;

    @Nullable
    private ObjectName objectName;

    private boolean useStrictCasing = true;

    @Nullable
    private Class<?> managementInterface;

    @Nullable
    private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

    private final ConnectorDelegate connector = new ConnectorDelegate();

    @Nullable
    private MBeanServerConnection serverToUse;

    @Nullable
    private MBeanServerInvocationHandler invocationHandler;

    private Map<String, MBeanAttributeInfo> allowedAttributes = Collections.emptyMap();

    private Map<MethodCacheKey, MBeanOperationInfo> allowedOperations = Collections.emptyMap();

    private final Map<Method, String[]> signatureCache = new HashMap<>();

    private final Object preparationMonitor = new Object();


    /**
     * Set the {@code MBeanServerConnection} used to connect to the
     * MBean which all invocations are routed to.
     */
    public void setServer(MBeanServerConnection server) {
        this.server = server;
    }

    /**
     * Set the service URL of the remote {@code MBeanServer}.
     */
    public void setServiceUrl(String url) throws MalformedURLException {
        this.serviceUrl = new JMXServiceURL(url);
    }

    /**
     * Specify the environment for the JMX connector.
     *
     * @see javax.management.remote.JMXConnectorFactory#connect(javax.management.remote.JMXServiceURL, java.util.Map)
     */
    public void setEnvironment(@Nullable Map<String, ?> environment) {
        this.environment = environment;
    }

    /**
     * Allow Map access to the environment to be set for the connector,
     * with the option to add or override specific entries.
     * <p>Useful for specifying entries directly, for example via
     * "environment[myKey]". This is particularly useful for
     * adding or overriding entries in child bean definitions.
     */
    @Nullable
    public Map<String, ?> getEnvironment() {
        return this.environment;
    }

    /**
     * Set the agent id of the {@code MBeanServer} to locate.
     * <p>Default is none. If specified, this will result in an
     * attempt being made to locate the attendant MBeanServer, unless
     * the {@link #setServiceUrl "serviceUrl"} property has been set.
     *
     * @see javax.management.MBeanServerFactory#findMBeanServer(String)
     * <p>Specifying the empty String indicates the platform MBeanServer.
     */
    public void setAgentId(String agentId) {
        this.agentId = agentId;
    }

    /**
     * Set whether or not the proxy should connect to the {@code MBeanServer}
     * at creation time ("true") or the first time it is invoked ("false").
     * Default is "true".
     */
    public void setConnectOnStartup(boolean connectOnStartup) {
        this.connectOnStartup = connectOnStartup;
    }

    /**
     * Set whether to refresh the MBeanServer connection on connect failure.
     * Default is "false".
     * <p>Can be turned on to allow for hot restart of the JMX server,
     * automatically reconnecting and retrying in case of an IOException.
     */
    public void setRefreshOnConnectFailure(boolean refreshOnConnectFailure) {
        this.refreshOnConnectFailure = refreshOnConnectFailure;
    }

    /**
     * Set the {@code ObjectName} of the MBean which calls are routed to,
     * as {@code ObjectName} instance or as {@code String}.
     */
    public void setObjectName(Object objectName) throws MalformedObjectNameException {
        this.objectName = ObjectNameManager.getInstance(objectName);
    }

    /**
     * Set whether to use strict casing for attributes. Enabled by default.
     * <p>When using strict casing, a JavaBean property with a getter such as
     * {@code getFoo()} translates to an attribute called {@code Foo}.
     * With strict casing disabled, {@code getFoo()} would translate to just
     * {@code foo}.
     */
    public void setUseStrictCasing(boolean useStrictCasing) {
        this.useStrictCasing = useStrictCasing;
    }

    /**
     * Set the management interface of the target MBean, exposing bean property
     * setters and getters for MBean attributes and conventional Java methods
     * for MBean operations.
     */
    public void setManagementInterface(@Nullable Class<?> managementInterface) {
        this.managementInterface = managementInterface;
    }

    /**
     * Return the management interface of the target MBean,
     * or {@code null} if none specified.
     */
    @Nullable
    protected final Class<?> getManagementInterface() {
        return this.managementInterface;
    }

    @Override
    public void setBeanClassLoader(ClassLoader beanClassLoader) {
        this.beanClassLoader = beanClassLoader;
    }


    /**
     * Prepares the {@code MBeanServerConnection} if the "connectOnStartup"
     * is turned on (which it is by default).
     */
    @Override
    public void afterPropertiesSet() {
        if (this.server != null && this.refreshOnConnectFailure) {
            throw new IllegalArgumentException("'refreshOnConnectFailure' does not work when setting " +
                    "a 'server' reference. Prefer 'serviceUrl' etc instead.");
        }
        if (this.connectOnStartup) {
            prepare();
        }
    }

    /**
     * Ensures that an {@code MBeanServerConnection} is configured and attempts
     * to detect a local connection if one is not supplied.
     */
    public void prepare() {
        synchronized (this.preparationMonitor) {
            if (this.server != null) {
                this.serverToUse = this.server;
            } else {
                this.serverToUse = null;
                this.serverToUse = this.connector.connect(this.serviceUrl, this.environment, this.agentId);
            }
            this.invocationHandler = null;
            if (this.useStrictCasing) {
                Assert.state(this.objectName != null, "No ObjectName set");
                // Use the JDK's own MBeanServerInvocationHandler, in particular for native MXBean support.
                this.invocationHandler = new MBeanServerInvocationHandler(this.serverToUse, this.objectName,
                        (this.managementInterface != null && JMX.isMXBeanInterface(this.managementInterface)));
            } else {
                // Non-strict casing can only be achieved through custom invocation handling.
                // Only partial MXBean support available!
                retrieveMBeanInfo(this.serverToUse);
            }
        }
    }

    /**
     * Loads the management interface info for the configured MBean into the caches.
     * This information is used by the proxy when determining whether an invocation matches
     * a valid operation or attribute on the management interface of the managed resource.
     */
    private void retrieveMBeanInfo(MBeanServerConnection server) throws MBeanInfoRetrievalException {
        try {
            MBeanInfo info = server.getMBeanInfo(this.objectName);

            MBeanAttributeInfo[] attributeInfo = info.getAttributes();
            this.allowedAttributes = new HashMap<>(attributeInfo.length);
            for (MBeanAttributeInfo infoEle : attributeInfo) {
                this.allowedAttributes.put(infoEle.getName(), infoEle);
            }

            MBeanOperationInfo[] operationInfo = info.getOperations();
            this.allowedOperations = new HashMap<>(operationInfo.length);
            for (MBeanOperationInfo infoEle : operationInfo) {
                Class<?>[] paramTypes = JmxUtils.parameterInfoToTypes(infoEle.getSignature(), this.beanClassLoader);
                this.allowedOperations.put(new MethodCacheKey(infoEle.getName(), paramTypes), infoEle);
            }
        } catch (ClassNotFoundException ex) {
            throw new MBeanInfoRetrievalException("Unable to locate class specified in method signature", ex);
        } catch (IntrospectionException ex) {
            throw new MBeanInfoRetrievalException("Unable to obtain MBean info for bean [" + this.objectName + "]", ex);
        } catch (InstanceNotFoundException ex) {
            // if we are this far this shouldn't happen, but...
            throw new MBeanInfoRetrievalException("Unable to obtain MBean info for bean [" + this.objectName +
                    "]: it is likely that this bean was unregistered during the proxy creation process",
                    ex);
        } catch (ReflectionException ex) {
            throw new MBeanInfoRetrievalException("Unable to read MBean info for bean [ " + this.objectName + "]", ex);
        } catch (IOException ex) {
            throw new MBeanInfoRetrievalException("An IOException occurred when communicating with the " +
                    "MBeanServer. It is likely that you are communicating with a remote MBeanServer. " +
                    "Check the inner exception for exact details.", ex);
        }
    }

    /**
     * Return whether this client interceptor has already been prepared,
     * i.e. has already looked up the server and cached all metadata.
     */
    protected boolean isPrepared() {
        synchronized (this.preparationMonitor) {
            return (this.serverToUse != null);
        }
    }


    /**
     * Route the invocation to the configured managed resource..
     *
     * @param invocation the {@code MethodInvocation} to re-route
     * @return the value returned as a result of the re-routed invocation
     * @throws Throwable an invocation error propagated to the user
     * @see #doInvoke
     * @see #handleConnectFailure
     */
    @Override
    @Nullable
    public Object invoke(MethodInvocation invocation) throws Throwable {
        // Lazily connect to MBeanServer if necessary.
        synchronized (this.preparationMonitor) {
            if (!isPrepared()) {
                prepare();
            }
        }
        try {
            return doInvoke(invocation);
        } catch (MBeanConnectFailureException ex) {
            return handleConnectFailure(invocation, ex);
        } catch (IOException ex) {
            return handleConnectFailure(invocation, ex);
        }
    }

    /**
     * Refresh the connection and retry the MBean invocation if possible.
     * <p>If not configured to refresh on connect failure, this method
     * simply rethrows the original exception.
     *
     * @param invocation the invocation that failed
     * @param ex         the exception raised on remote invocation
     * @return the result value of the new invocation, if succeeded
     * @throws Throwable an exception raised by the new invocation,
     *                   if it failed as well
     * @see #setRefreshOnConnectFailure
     * @see #doInvoke
     */
    @Nullable
    protected Object handleConnectFailure(MethodInvocation invocation, Exception ex) throws Throwable {
        if (this.refreshOnConnectFailure) {
            String msg = "Could not connect to JMX server - retrying";
            if (logger.isDebugEnabled()) {
                logger.warn(msg, ex);
            } else if (logger.isWarnEnabled()) {
                logger.warn(msg);
            }
            prepare();
            return doInvoke(invocation);
        } else {
            throw ex;
        }
    }

    /**
     * Route the invocation to the configured managed resource. Correctly routes JavaBean property
     * access to {@code MBeanServerConnection.get/setAttribute} and method invocation to
     * {@code MBeanServerConnection.invoke}.
     *
     * @param invocation the {@code MethodInvocation} to re-route
     * @return the value returned as a result of the re-routed invocation
     * @throws Throwable an invocation error propagated to the user
     */
    @Nullable
    protected Object doInvoke(MethodInvocation invocation) throws Throwable {
        Method method = invocation.getMethod();
        try {
            Object result;
            if (this.invocationHandler != null) {
                result = this.invocationHandler.invoke(invocation.getThis(), method, invocation.getArguments());
            } else {
                PropertyDescriptor pd = BeanUtils.findPropertyForMethod(method);
                if (pd != null) {
                    result = invokeAttribute(pd, invocation);
                } else {
                    result = invokeOperation(method, invocation.getArguments());
                }
            }
            return convertResultValueIfNecessary(result, new MethodParameter(method, -1));
        } catch (MBeanException ex) {
            throw ex.getTargetException();
        } catch (RuntimeMBeanException ex) {
            throw ex.getTargetException();
        } catch (RuntimeErrorException ex) {
            throw ex.getTargetError();
        } catch (RuntimeOperationsException ex) {
            // This one is only thrown by the JMX 1.2 RI, not by the JDK 1.5 JMX code.
            RuntimeException rex = ex.getTargetException();
            if (rex instanceof RuntimeMBeanException) {
                throw ((RuntimeMBeanException) rex).getTargetException();
            } else if (rex instanceof RuntimeErrorException) {
                throw ((RuntimeErrorException) rex).getTargetError();
            } else {
                throw rex;
            }
        } catch (OperationsException ex) {
            if (ReflectionUtils.declaresException(method, ex.getClass())) {
                throw ex;
            } else {
                throw new InvalidInvocationException(ex.getMessage());
            }
        } catch (JMException ex) {
            if (ReflectionUtils.declaresException(method, ex.getClass())) {
                throw ex;
            } else {
                throw new InvocationFailureException("JMX access failed", ex);
            }
        } catch (IOException ex) {
            if (ReflectionUtils.declaresException(method, ex.getClass())) {
                throw ex;
            } else {
                throw new MBeanConnectFailureException("I/O failure during JMX access", ex);
            }
        }
    }

    @Nullable
    private Object invokeAttribute(PropertyDescriptor pd, MethodInvocation invocation)
            throws JMException, IOException {

        Assert.state(this.serverToUse != null, "No MBeanServerConnection available");

        String attributeName = JmxUtils.getAttributeName(pd, this.useStrictCasing);
        MBeanAttributeInfo inf = this.allowedAttributes.get(attributeName);
        // If no attribute is returned, we know that it is not defined in the
        // management interface.
        if (inf == null) {
            throw new InvalidInvocationException(
                    "Attribute '" + pd.getName() + "' is not exposed on the management interface");
        }

        if (invocation.getMethod().equals(pd.getReadMethod())) {
            if (inf.isReadable()) {
                return this.serverToUse.getAttribute(this.objectName, attributeName);
            } else {
                throw new InvalidInvocationException("Attribute '" + attributeName + "' is not readable");
            }
        } else if (invocation.getMethod().equals(pd.getWriteMethod())) {
            if (inf.isWritable()) {
                this.serverToUse.setAttribute(this.objectName, new Attribute(attributeName, invocation.getArguments()[0]));
                return null;
            } else {
                throw new InvalidInvocationException("Attribute '" + attributeName + "' is not writable");
            }
        } else {
            throw new IllegalStateException(
                    "Method [" + invocation.getMethod() + "] is neither a bean property getter nor a setter");
        }
    }

    /**
     * Routes a method invocation (not a property get/set) to the corresponding
     * operation on the managed resource.
     *
     * @param method the method corresponding to operation on the managed resource.
     * @param args   the invocation arguments
     * @return the value returned by the method invocation.
     */
    private Object invokeOperation(Method method, Object[] args) throws JMException, IOException {
        Assert.state(this.serverToUse != null, "No MBeanServerConnection available");

        MethodCacheKey key = new MethodCacheKey(method.getName(), method.getParameterTypes());
        MBeanOperationInfo info = this.allowedOperations.get(key);
        if (info == null) {
            throw new InvalidInvocationException("Operation '" + method.getName() +
                    "' is not exposed on the management interface");
        }

        String[] signature;
        synchronized (this.signatureCache) {
            signature = this.signatureCache.get(method);
            if (signature == null) {
                signature = JmxUtils.getMethodSignature(method);
                this.signatureCache.put(method, signature);
            }
        }

        return this.serverToUse.invoke(this.objectName, method.getName(), args, signature);
    }

    /**
     * Convert the given result object (from attribute access or operation invocation)
     * to the specified target class for returning from the proxy method.
     *
     * @param result    the result object as returned by the {@code MBeanServer}
     * @param parameter the method parameter of the proxy method that's been invoked
     * @return the converted result object, or the passed-in object if no conversion
     * is necessary
     */
    @Nullable
    protected Object convertResultValueIfNecessary(@Nullable Object result, MethodParameter parameter) {
        Class<?> targetClass = parameter.getParameterType();
        try {
            if (result == null) {
                return null;
            }
            if (ClassUtils.isAssignableValue(targetClass, result)) {
                return result;
            }
            if (result instanceof CompositeData) {
                Method fromMethod = targetClass.getMethod("from", CompositeData.class);
                return ReflectionUtils.invokeMethod(fromMethod, null, result);
            } else if (result instanceof CompositeData[]) {
                CompositeData[] array = (CompositeData[]) result;
                if (targetClass.isArray()) {
                    return convertDataArrayToTargetArray(array, targetClass);
                } else if (Collection.class.isAssignableFrom(targetClass)) {
                    Class<?> elementType =
                            ResolvableType.forMethodParameter(parameter).asCollection().resolveGeneric();
                    if (elementType != null) {
                        return convertDataArrayToTargetCollection(array, targetClass, elementType);
                    }
                }
            } else if (result instanceof TabularData) {
                Method fromMethod = targetClass.getMethod("from", TabularData.class);
                return ReflectionUtils.invokeMethod(fromMethod, null, result);
            } else if (result instanceof TabularData[]) {
                TabularData[] array = (TabularData[]) result;
                if (targetClass.isArray()) {
                    return convertDataArrayToTargetArray(array, targetClass);
                } else if (Collection.class.isAssignableFrom(targetClass)) {
                    Class<?> elementType =
                            ResolvableType.forMethodParameter(parameter).asCollection().resolveGeneric();
                    if (elementType != null) {
                        return convertDataArrayToTargetCollection(array, targetClass, elementType);
                    }
                }
            }
            throw new InvocationFailureException(
                    "Incompatible result value [" + result + "] for target type [" + targetClass.getName() + "]");
        } catch (NoSuchMethodException ex) {
            throw new InvocationFailureException(
                    "Could not obtain 'from(CompositeData)' / 'from(TabularData)' method on target type [" +
                            targetClass.getName() + "] for conversion of MXBean data structure [" + result + "]");
        }
    }

    private Object convertDataArrayToTargetArray(Object[] array, Class<?> targetClass) throws NoSuchMethodException {
        Class<?> targetType = targetClass.getComponentType();
        Method fromMethod = targetType.getMethod("from", array.getClass().getComponentType());
        Object resultArray = Array.newInstance(targetType, array.length);
        for (int i = 0; i < array.length; i++) {
            Array.set(resultArray, i, ReflectionUtils.invokeMethod(fromMethod, null, array[i]));
        }
        return resultArray;
    }

    private Collection<?> convertDataArrayToTargetCollection(Object[] array, Class<?> collectionType, Class<?> elementType)
            throws NoSuchMethodException {

        Method fromMethod = elementType.getMethod("from", array.getClass().getComponentType());
        Collection<Object> resultColl = CollectionFactory.createCollection(collectionType, Array.getLength(array));
        for (int i = 0; i < array.length; i++) {
            resultColl.add(ReflectionUtils.invokeMethod(fromMethod, null, array[i]));
        }
        return resultColl;
    }


    @Override
    public void destroy() {
        this.connector.close();
    }


    /**
     * Simple wrapper class around a method name and its signature.
     * Used as the key when caching methods.
     */
    private static final class MethodCacheKey implements Comparable<MethodCacheKey> {

        private final String name;

        private final Class<?>[] parameterTypes;

        /**
         * Create a new instance of {@code MethodCacheKey} with the supplied
         * method name and parameter list.
         *
         * @param name           the name of the method
         * @param parameterTypes the arguments in the method signature
         */
        public MethodCacheKey(String name, @Nullable Class<?>[] parameterTypes) {
            this.name = name;
            this.parameterTypes = (parameterTypes != null ? parameterTypes : new Class<?>[0]);
        }

        @Override
        public boolean equals(Object other) {
            if (this == other) {
                return true;
            }
            MethodCacheKey otherKey = (MethodCacheKey) other;
            return (this.name.equals(otherKey.name) && Arrays.equals(this.parameterTypes, otherKey.parameterTypes));
        }

        @Override
        public int hashCode() {
            return this.name.hashCode();
        }

        @Override
        public String toString() {
            return this.name + "(" + StringUtils.arrayToCommaDelimitedString(this.parameterTypes) + ")";
        }

        @Override
        public int compareTo(MethodCacheKey other) {
            int result = this.name.compareTo(other.name);
            if (result != 0) {
                return result;
            }
            if (this.parameterTypes.length < other.parameterTypes.length) {
                return -1;
            }
            if (this.parameterTypes.length > other.parameterTypes.length) {
                return 1;
            }
            for (int i = 0; i < this.parameterTypes.length; i++) {
                result = this.parameterTypes[i].getName().compareTo(other.parameterTypes[i].getName());
                if (result != 0) {
                    return result;
                }
            }
            return 0;
        }
    }

}
